Wax crayons have long been used by children (and others) for drawing and generally as writing instruments. Over the years, many different types of pigments have been incorporated into a wax base to generate a complete array of available colors. Such wax crayons have had limited application for serious artistic expressions, because on the one hand, the line created by a crayon is not very precise, and on the other hand, the pigmented wax does not readily lend itself to blending of the colors. In order to achieve blendability, artists have been forced to switch to a different medium such as pastels, paints, and the like.
U.S. Pat. No. 3,769,045 discloses a process for producing a liquid-write crayon. This crayon is designed to have a low wax content so that the crayon approaches the desirable fluid marking properties of felt-tip markers. To achieve this goal, the crayon contains 20 to 40 weight percent wax and 60 to 80 weight percent encapsulated marking liquid. The marking liquid contained within the microcapsules is disclosed to be any liquid dye or ink, but if desired may be colorless, but colorable. An example of a colorless but colorable marking liquid is the class of acidic mark-forming materials commonly used in the carbonless paper industry. The ink or dye contained in the microcapsules may optionally be dissolved in a liquid oil of a viscosity to act as an ink vehicle.
U.S. Pat. No. 5,039,243 to O'Brien discloses crayons that are provided with microcapsules containing fragrant materials within the shell of the microcapsules. Applying the crayon to a surface as in coloring a picture ruptures some of the microcapsules and releases a fragrance. The microcapsules may constitute between 1 and 60 percent of the weight of the crayons.